| Summary: | This thesis is concerned with the quantitative study of the geometrical asymmetry and velocity asymmetry associated with shallow water oscillatory waves. The region of interest in the work is the shallow water zone defined by the depth to wave length ratio d 40-15, including the breaker-zone. Three descriptions of wave asymmetry are defined and examined: 1) wave vertical asymmetry, 2) wave slope asymmetry, and 3) wave horizontal asymmetry. Two methods of defining horizontal velocity asymmetry are investigated, namely: 1) horizontal velocity (magnitude) asymmetry, and 2) horizontal velocity (time) asymmetry. The effects of shoaling, produced by beaches of different slope, on the wave asymmetry and the velocity fields are examined. Six beach slopes in the range 1:4 to 1:18 were employed, and a quantitative correlation was found to exist between the wave slope asymmetry, wave horizontal asymmetry and the wave vertical asymmetry, as well as between the wave asymmetry and the velocity asymmetry. General expressions are given on the basis of existing wave theories for the wave horizontal asymmetry and the horizontal velocity (magnitude) asymmetry. A detailed study was made of the effect of the backwash of the wave on the wave asymmetry and the velocity fields seaward of the breakers. The mechanics of sediment movement under the action of waves is discussed in the light of the time-history of the velocity curves. Finally a preliminary investigation of the effect of the phase-difference of uprush and backwash on the wave motion at the breaker position was made. This involved systematic variation of the incident wave characteristics in order to obtain different breaker types.
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